News Column

Researchers Submit Patent Application, "Combination Touch and Transducer Input System and Method", for Approval

August 21, 2014



By a News Reporter-Staff News Editor at Computer Weekly News -- From Washington, D.C., VerticalNews journalists report that a patent application by the inventors King-Smith, Oliver P. (Aptos, CA); Smit, Bernardus H. (San Jose, CA); Hadizad, Peyman (Redwood City, CA), filed on March 27, 2014, was made available online on August 7, 2014.

The patent's assignee is Wacom Co., Ltd.

News editors obtained the following quote from the background information supplied by the inventors: "A variety of different types of input devices are commonly used in a variety of different electronic systems, including computers (e.g., laptop computers, tablet computers, personal digital assistants) and communication devices (e.g., mobile phones, wireless handheld communication devices). One type of input device is generally referred to as a touch sensor or proximity sensor. A touch sensor uses a variety of different techniques to determine the position of proximate objects, such as fingers. For example, capacitive touch sensors determine the position of proximate objects by determining a change in capacitance that occurs due to the presence of proximate objects. Another type of input device is commonly referred to as a digitizer tablet, but also referred to as a graphics tablet, graphics pad, or drawing tablet. Digitizer tablets include a sensing surface upon which a user can enter input using a transducer, typically implemented as a stylus or other pen-like drawing apparatus. In typical digitizers, the transducer emits an electromagnetic signal, which is detected by the sensing surface. The electromagnetic signal detected by the sensing surface is then used and processed to determine the position of the transducer.

"In general, digitizers offer increased position-detection accuracy and resolution when compared to typical touch sensors. Digitizers typically require the use of a specialized transducer for inputting. It has been desirable to combine the attributes (e.g., convenience) of touch sensors with the improved accuracy and resolution of digitizers. Unfortunately, combination touch sensor-digitizers have had limited applicability, mainly due to high cost and complexity associated with implementation, the additional three-dimensional space required to accommodate the combination, and the requirement for special types of displays that could support both touch sensing and transducer (e.g., stylus) sensing. Thus, there remains a continuing need for improved combination touch sensor and transducer-based input devices."

As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "This summary is provided to introduce a selection of concepts in a simplified form that is further described below in the Detailed Description. This summary is not intended to identify key features of the claimed subject matter nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

"The embodiments of the invention provide systems and methods for facilitating user input into an electronic system. Combination touch and transducer input systems are provided, which facilitate user input both with ordinary objects (e.g., fingers) and with transducers that emit an electric field for position detection.

"According to one aspect of the invention, a combination touch and transducer input system is provided, which includes a transducer (e.g., a stylus), an array of electrodes, and a controller coupled to the array of electrodes. The array of electrodes and the controller together form a sensor that is used for detecting both the position of a proximate object, such as a finger, and the position of the transducer. The transducer is typically in the form of a stylus or other pen-like apparatus, and is configured to generate an electric field. The controller of the sensor is configured to operate in a proximate object sensing mode (hereinafter the 'touch mode') and in a transducer sensing mode (hereinafter the 'transducer mode'), either simultaneously or in an alternating manner by switching between the two modes in successive sampling periods.

"When operating in the touch mode, the controller determines the position(s) of one or more proximate objects (e.g., fingers) by capacitively sensing the object(s) with the array of electrodes. In one example, the controller determines the position of each object by detecting a change in capacitance caused by that object in the array of electrodes. When operating in the transducer mode, the controller determines a position of the transducer by measuring attributes (e.g., amplitudes, phases, etc.) of a plurality of sensing signals that are induced in the array of electrodes by the electric field generated by the transducer. Specifically, as the transducer (an antenna) and each of the array of electrodes are capacitively coupled, the controller determines the position of the transducer by measuring a charge induced at each of the array of electrodes.

"The transducer is further configured to send digital data to the sensor. For example, the transducer may include electronic circuitry (e.g., a microcontroller unit (MCU) or microprocessor) configured to encode digital data in the electric field for transmission to the array of electrodes, and the controller of the sensor is configured to decode the digital data received by the array of electrodes. For example, the digital data may include data related to the transducer's pen tip pressure, the transducer's switch status, or the transducer's unique ID.

"According to another aspect of the invention, the transducer is configured to selectively generate an electric field at multiple frequencies and to encode digital data in frequency shifts of the generated electric field, while the controller is configured to detect the plurality of sensing signals at multiple frequencies and to decode the digital data encoded in the frequency shifts. The multiple frequencies may be determined, for example, by dividing down a base frequency, so as to avoid harmonics generated by any signal transmitted by the transducer. Any suitable Frequency-Shift Keying (FSK) technique, including the Manchester coding scheme, may be used to encode digital data. According to a further aspect of the invention, any other digital modulation technique may be used to encode digital data, including Amplitude-Shift Keying (ASK) technique, Phase-Shift Keying (PSK) technique, and Quadrature Amplitude Modulation (QAM) technique.

"In accordance with another aspect of the invention, the digital data transmission may be bi-directional. That is, in addition to the transducer transmitting digital data to the controller, the controller may be configured to transmit digital data to the transducer.

"According to one aspect of the invention, the transducer and the controller communicate asynchronously.

"According to one aspect of the invention, the transducer is configured to selectively generate the electric field at multiple frequencies and the controller is further configured to select one (or more) of the multiple frequency channels as receiving channel(s). For example, the controller may determine a signal-to-noise ratio for each frequency channel and select the frequency channel having the highest signal-to-noise ratio as the receiving channel. According to a further aspect of the invention, when two or more combination touch and transducer input systems are provided, the transducer of the first system is configured to generate the electric field at a first frequency (or a first set of frequencies) and the transducer of the second system is configured to generate the electric field at a second frequency (or a second set of frequencies) different from the first frequency (or the first set of frequencies), to avoid cross-coupling between the two systems that may be used proximate to each other.

"According to one aspect of the invention, the array of electrodes includes a first set of elongate electrodes arranged substantially in parallel with each other and extending in a first direction and a second set of elongate electrodes arranged substantially in parallel with each other and extending in a second direction that is different from the first direction. For example, the first and second directions may be generally perpendicular to each other. Each pair of at least one of the first set of elongate electrodes and at least one of the second set of elongate electrodes forms a capacitor. When operating in the touch mode, the controller is configured to supply a signal to each of the first set of elongate electrodes, detect a capacitance change reflected in a signal outputted from each of the second set of elongate electrodes, and determine the position of the proximate object based on the detected capacitance change.

"When operating in the transducer mode using the electric field coupling, the controller is configured to measure attributes (e.g., amplitudes and phases) of a plurality of sensing signals outputted from both the first and second sets of elongate electrodes and calculate the position of the transducer based on the measured attributes. According to a further aspect of the invention, when operating in the transducer mode, the controller is configured to measure an attribute of a sensing signal outputted from each of the first or second set of elongate electrodes while selectively terminating (e.g., floating, terminating via a resistor to ground, or grounding) two or more of the first or second set of elongate electrodes that are adjacent to that elongate electrode being sensed, to thereby improve the quality of the sensing signal.

"According to one aspect of the invention, the controller is configured to alternate between operating in the touch mode and operating in the transducer mode in successive sampling periods of the system. According to another aspect of the invention, the operating mode may be selected by a user of the system. According to a further aspect of the invention, the controller is configured to selectively divide the array of electrodes into a touch mode section and a transducer mode section, and to simultaneously operate in the touch mode in the touch mode section and in the transducer mode in the transducer mode section. The touch mode section may consist of a plurality of touch mode sub-sections, while the transducer mode section may consist of a plurality of transducer mode sub-sections. According to a still further aspect of the invention, the controller periodically switches the touch mode section and the transducer mode section such that a given point on the array of electrodes alternates between being in the touch mode section and being in the transducer mode section.

"According to one aspect of the invention, the controller includes a cascoded transimpedance amplifier coupled to the array of electrodes. The cascoded transimpedance amplifier is configured to amplify the plurality of sensing signals induced by the electric field in the array of electrodes, while advantageously isolating the input capacitance of the array of electrodes from the feedback resistor of the transimpedance amplifier.

"According to one aspect of the invention, the transducer includes a capacitor or a battery that is configured to function as a power supply for the transducer.

"According to a further aspect of the invention, the controller is configured to determine the position of the transducer by fitting the measured attributes (e.g., amplitudes, phases, etc.) of the plurality of sensing signals to a pre-determined parameterized curve. According to one aspect of the invention, the pre-determined parameterized curve relates a plurality of positions of the transducer relative to one electrode with a plurality of attributes of sensing signals induced in that electrode by the transducer at the plurality of positions, respectively. According to one aspect of the invention, the pre-determined parameterized curve is empirically derived for use with the transducer having a particular tip shape and the array of electrodes having a particular electrode configuration pattern. According to one aspect of the invention, the pre-determined parameterized curve includes a position parameter and at least one or more of a height parameter and a tilt parameter. According to one aspect of the invention, the system further comprises an external processor, such as a processor in a host system (e.g., a PC that includes the combination touch and transducer input system), and the controller and the external processor perform the curve fitting operation, which may be computationally intensive, in distributed processing.

"According to another aspect of the invention, a cordless transducer is provided, which is configured for use with an array of electrodes, wherein the cordless transducer and the array of electrodes are capacitively coupled. The cordless transducer includes a pen-shaped housing including a pen tip at its distal end, and a transducer controller arranged within the pen-shaped housing. The transducer controller controls the operation of the cordless transducer, and includes a pressure sensor for detecting the pressure applied to the pen tip. The cordless transducer also includes an antenna coupled to the transducer controller to transmit the pressure sensor data, which is detected by the pressure sensor, as digital data to the array of electrodes. The transducer controller includes a power storage device, such as a battery or a capacitor, which supplies power to drive the transducer controller, to thereby achieve the cordless transducer.

"According to another aspect of the invention, a combination touch and transducer input system is provided, which includes a cordless transducer described above, and a sensor. The sensor includes an array of electrodes and a sensor controller coupled to the array of electrodes. The sensor controller is configured to operate in both a touch mode to determine a position of a proximate object by capacitively sensing the object with the array of electrodes, and in a transducer mode to determine a position of the cordless transducer by measuring attributes of a plurality of sensing signals induced in the array of electrodes by the electric field generated by the cordless transducer. The cordless transducer transmits pressure sensor data as digital data to the sensor.

"According to a further aspect of the invention, a method is provided for selectively determining a position of a proximate object and a position of a transducer. The method includes eight steps. First, a proximate object is capacitively sensed with an array of electrodes. Second, a position of the proximate object is determined based on the capacitive sensing. Third, an electric field is generated with the transducer. Fourth, digital data is transmitted from the transducer. Fifth, a plurality of sensing signals are induced based on the electric field in a corresponding plurality of electrodes in the array of electrodes. Sixth, attributes of the plurality of sensing signals are measured. Seventh, a position of the transducer is determined based on the measured attributes of the plurality of sensing signals. Eighth, the digital data is received with the array of electrodes.

DESCRIPTION OF THE DRAWINGS

"The present invention may more readily be understood by reference to the accompanying drawings in which:

"FIG. 1 shows a tablet computer, which includes a combination touch and transducer input system in accordance with an embodiment of the invention;

"FIG. 2 is schematic representation of a sensor for use in a combination touch and transducer input system, the sensor including a controller and an array of electrodes, in accordance with an embodiment of the invention;

"FIGS. 3A and 3B are schematic representations of a transducer for use in a combination touch and transducer input system, in accordance with an embodiment of the invention;

"FIG. 4 is a block diagram of a transducer in accordance with an embodiment of the invention;

"FIG. 5A is a block diagram of a sensor, including a controller and an array of electrodes, in accordance with an embodiment of the invention;

"FIG. 5B is a schematic representation of an array of electrodes that is divided into one or more touch mode sections and one or more transducer mode sections, according to one embodiment of the invention;

"FIG. 6 is a block diagram of a processing stage, which may be included in the controller of FIG. 5A, in accordance with an embodiment of the invention;

"FIG. 7 is a circuit representation of a charge amplifier, which may be included in the processing stage of FIG. 6, in accordance with an embodiment of the invention;

"FIG. 8 is a circuit representation of a voltage amplifier, which may be included in the processing stage of FIG. 6, in accordance with an embodiment of the invention;

"FIG. 9 is a circuit representation of a transimpedance amplifier, which may be included in the processing stage of FIG. 6, in accordance with an embodiment of the invention;

"FIG. 10 is a circuit representation of a cascoded transimpedance amplifier, which may be included in the processing stage of FIG. 6, in accordance with an embodiment of the invention;

"FIG. 11A is a flow chart illustrating a process of scanning an array of electrodes during a transducer mode, according to one embodiment of the invention;

"FIGS. 11B and 11C each illustrate an array of electrodes, in which when one elongate electrode is sensed during a transducer mode using the electric field coupling, two ore more of the elongate electrodes adjacent to the electrode being sensed are selectively terminated (e.g., floated, terminated via a resistor to ground, or grounded) according to one embodiment of the invention;

"FIG. 11D illustrates an array of electrodes suitably arranged to pick up a magnetic field component of an electromagnetic field generated by a transducer, during the transducer mode, in accordance with one embodiment of the present invention;

"FIG. 12 is a schematic representation of a digital filtering procedure according to one embodiment of the invention;

"FIG. 13A is a flow chart illustrating a sample process used to determine a position of a transducer based on a curve-fitting technique, according to one embodiment of the invention;

"FIG. 13B is a sample parameterized curve that is empirically derived and used to determine the position of a transducer, according to one embodiment of the invention;

"FIG. 13C is a sample phase locked loop (PLL) circuit suitable for generating multiple frequencies for use in accordance with one embodiment of the invention;

"FIG. 14 shows a sample data frame used to transmit digital data between a transducer and a sensor in a combination touch and transducer input system, according to one embodiment of the invention;

"FIG. 15 is a flow chart illustrating a process performed by a transducer, including the process of encoding and transmitting digital data to a sensor, according to one embodiment of the invention; and

"FIG. 16 is a flow chart illustrating a process of decoding digital data encoded in frequency shifts of a signal generated by a transducer, according to one embodiment of the invention."

For additional information on this patent application, see: King-Smith, Oliver P.; Smit, Bernardus H.; Hadizad, Peyman. Combination Touch and Transducer Input System and Method. Filed March 27, 2014 and posted August 7, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=4889&p=98&f=G&l=50&d=PG01&S1=20140731.PD.&OS=PD/20140731&RS=PD/20140731

Keywords for this news article include: Wacom Co. Ltd.

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